A liquid crystal display generally comprises a polarizing plate and a liquid crystal cell. For ensuring the quality of displayed images, the viewing angle must be enlarged and the display surface (screen) must be prevented from reflecting light coming from outside.
The most widely used display is a TFT liquid crystal display of TN mode, in which an optical compensatory sheet is provided between the polarizing plate and the liquid crystal cell. As described in Japanese Patent Provisional Publication Nos. 8(1996)-50206, 7(1995)-191217 and European Patent No. 0911656A2, the TFT liquid crystal display of TN mode gives an image of high quality within a wide viewing angle range. However, gradation of an image displayed by the TFT liquid crystal display is often inverted when the screen is seen downward.
To solve the problem, various proposals have been given. For example, it has been proposed that a diffusing means (Japanese Patent No. 2,822,983), an optical axis-exchanger (Japanese Patent Publication No. 2001-33783) or an optical means for diffusing emitted light (Japanese Patent Publication No. 2001-56461) be provided on the observer side surface to improve the image quality remarkably. However, in these methods, it is necessary to use a diffusing means having highly controlled lens or diffraction grating structure, which costs a lot and is very difficult to mass-produce.
Japanese Patent Provisional Publication Nos. 6(1994)-18706 and 10(1998)-20103 disclose a diffusion film in which a transparent substrate is coated with a resin containing filler (e.g., silicone dioxide (silica)). That diffusion film can be mass-produced at low cost.
Japanese Patent Provisional Publication Nos. 11(1999)-160505, 11(1999)-305010, 11(1999)-326608, 2000-121809, 2000-180611 and 2000-338310 disclose other diffusion films, but they cannot fully improve the image quality.
Recently, liquid crystal displays have been often used as monitors of enough fine pixels to display minute images. However, the monitors equipped with the diffusion films often display blurred images.
For preventing the display surface from reflecting light coming from outside, an anti-reflection film is generally provided. The anti-reflection film is placed on the top surface of the display, and causes optical interference to reduce reflectance so that the display screen may be prevented from reflecting surrounding scenes and thereby so that the contrast of displayed image may not impaired. However, the anti-reflection film by no means solves the problem of viewing angle (inversion of gradation), and therefore it has been wanted to provide an anti-reflection film which prevents well the display surface from reflecting light coming from outside and at the same time which solves the problem of viewing angle.